[Histopathologic problems in the classification of pancreatic carcinoma].

The major differences between the third and fourth edition of the classification of pancreatic carcinoma are that tumors of ductal origin are divided into intraductal tumors and invasive ductal carcinoma, and atypical hyperplasia is mentioned. A low papillary or flat carcinoma in the pancreatic duct which is regarded as an early feature of ductal adenocarcinoma is classified as an intraductal tumor. However, usage of this term is not suitable from the standpoint of the outline of pathology. Minimally invasive intraductal papillary-mucinous carcinoma is classified as an intraductal tumor instead of invasive ductal carcinoma. It is often argued that minimally invasive intraductal papillary-mucinous carcinomas and invasive carcinomas derived from intraductal papillary adenocarcinoma should be distinguished. An intraductal papillary-mucinous tumor represents cystic dilatation of the pancreatic duct due to mucin secretion and papillary projection and is sometimes misdiagnosed as a mucinous cystic tumor. However, the two tumors are different. This point should be revised in the next edition. The pathologic description of the classification of pancreatic carcinoma should reflect the exact pathophysiology of these tumors and be simple.